Other veins alterations

The Anglo-Saxons report other diseases, non-parasitic or of unknown cause, affecting the veins or contiguous tissues of lettuce leaves:

- disease Pink rib mainly affects mature "crisphead" lettuce, after harvest. As the name suggests, the nerve tissues of the outer leaves take on a rather unusual pink tint. The cause of this disease is not known. Low oxygen content and high temperatures in storage rooms increase damage. Another condition, also linked to the CO2 content of the storage rooms, is reported after harvest on the same type of salad: disease "Brown stain" . Brown, oval, rather dry lesions appear at the base of the leaves.
- The "vein browning" of the salad ("Rib blight", "Rib discoloration", "Brown rib") is materialized by a progressive blackening of the tissues located at the level of the main and secondary veins, especially of the outer leaves of the heart. The origin of this condition is unknown.
- The "rusty blotches" ( "Russet spotting") is mainly manifested during storage lettuce having undergone various stress field. Small, oval, dry lesions, 2 to 4 mm long, more or less cover the veins and blade, especially on the lower part of the leaves (Figures 2 and 3). The presence of ethylene and temperatures close to 5 ° C favor the appearance of these lesions.

It should be remembered that some herbicides can cause the appearance of necrotic alterations located on the main vein and secondary veins of lettuce (Figure 1). Check sheets Deformed leaves , chlorotic or yellow leaves and brown spots, black, more or less necrotic for more information about chemical injury.